Electrical system.



R. E. HELLMUND. ELECTRICAL SYSTEM.

APPLICATION FILED IYIAR. 4, I9I5.

1,300,388. Patented Apr. 15,1919.

2 SHE ETSSHEET I.

I WITNESSES:

, I I INVENTOR I v RudolfEHel/mun l. fiy w BY ATTORNEY R. E. HELLM UND.

ELECTRICAL SYSTEM.

APPLICATION FILED MAR-4.1915.

l ,SOO, 388, Patented Apr. '15, 1919.

2 SHEETS-SHEET 2.

WITNESS s: IINVENTOR h Rude/2Y5. He/lmund.

ATTORNEY UNITED STATES PATENT" OFFICE.

R'C'DOLF E HELLMUND, OF PITTSBURGH, PENNSYLVANI' A,ASSIGNOR T ESTINGHOUSE ELECTRIC AN'D MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRICAL SYSTEM.

To all whom it magj' concern:

Be it known that I, RUDoLr EQHELLMUND,

- a subject of the German Empire, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electrical Systems,

of which the following 7; a specification. I I

y invention relates to electrical systems, and. it'has special reference to systems of control for alternating-current railway electrifications of a certain type.

One-of the objects of my invention is to providea system of the above-indicated character which shall be adapted to prevent, automatically or otherwise, as desired, the total power absorbed by an alternatingcurrent railway system from exceeding a certain specified maximum at any time, with out, however, interfering undesirably with the operation of the several trains in operation during the period of incipient overload.

A further object of my invention is to provide a system in which, by varying the frequency of the output of a generator in a sub station, the power input thereto .may be satisfactory and may be efiiciently controlled, on the one hand, and a railway sys-- -tem that is fed from the station its.power demands desirably may have supplied at all times, on the other hand.

Another object of my invention is to provide apparatus of the class under consideration which shall eiiiciently, conveniently and reliably perform the intended functions at Y acomparatively small expense.

It is sometimes desirable, or even necessary, particularly in a case where a railway system purchases its power from an outside power company, that a' predetermined maximum consumption of power shall neverbe exceeded, even under unusually severe op-- eratmg conditions.

I It is especially toward means for preventing such an objectionable occurrence that my invention is directed; for, although, with an ideal distribution of trains, the power consumption maybe kept within the specified limit, it is evident that such an ideal condition cannot possibly be maintained'for any length of time.

- In a certain railway electrification, let it be assumed that-the general layout is as follows:

Specification of Letters Patent. Patented Apr, 15, 1919 Application. filed March 4, 1915. Serial No. 1 2,068.

to single-phase 25-cycle energy which, as isv well known, is better adapted for the propulsion of railway vehicles. Any suitable arrangement of power circuits and locomotives may be employed.

In order to meet the imposed condition 9f no excessive draft of ower from the cycle transmission mains, I have devised several relatively simple"sy'stems for performing the desired functions inexpensively, effectively and reliably. The following theoretical discussion will serve to render my invention more clearly understood.

The above-mentioned locomotives may operate on any frequency within a given range, providedithe voltage varies in proportion to the frequency. For example, if the frequency should-drop from the assumed normal value of 25 cycles to 20 or 15 cycles, and if the volts should decrease in the same pro portion,- the locomotive would .pperate under practically the. sametractive effort as before and with thesa'me current supplied to is transformed, by

the motors, but the input to the locomotive would be reduced practically to the frequency and voltage. in the event of an overload on the railway system, if the .fre uency delivered by the sub-station should e lowered, load might be reduced also.

the power, consumption from a circuit might be kept within in proportion In this way,

a specified maximum, but the train operation would be sacrificed. In other words, whereas the specified power consumption from the transmission circuit would not be exceeded, the

overload current demanded by the trains in order to maintain desirable operating conditions would not be Consequently supplied and the railway service would suffer in consequence.

the railway transmission However, if the output'of the frequency changer can be reduced in smaller proportion than the decrease-in frequency and volt- ,age or can be maintained substantially con.-

stant' during such decrease, then the demended overload current may be supplied I tothe railway system without exceeding the specified .power consumption from thetrans mission line and with good train operation.

changer can be held substantiallyconstant while the frequency and voltage .are decreased 30%, then the current delivered to the locomotives and their tracti-ve'effort can be increased approximately in proportion. Thus, with such a system, by varying the frequency but not varying the output in the same proportion, it becomes possible to haul heavier trains, or more of them, under overload conditions without exceeding the predetermined power input and, in addition, without sacrificing good train operation. Whereas, a system of this type 'is especially adapted for use with locomotives embody-' ing induction driving motors, it will be understood that the current regulation itself does not depend upon the use of such motors, and other systems employing such locomotives in part'or not at all may also secure a certain degree of benefit from the system.

In a co-pending application of Benjamin G. Lamme and Francis H. Shepard, Serial No. 808,716, filed December 26, 1913, and assigned to the Westinghouse Electric 85 Manufacturing Company, is shown and describeda system of the type under consideration, wherein the speed of the driving induction motor is varied, in accordance with load conditions, to permit of a corresponding variation of the delivered frequency and current from the generator that supplies energy to the railway line, whereby the desired results may be secured.

According to my present invention, I provide means for meeting the condition above referred to, comprising a system wherein the generated frequency and current may be varied, as desired, without changing the speed of the driving induction motor. One such system may include, in addition to a driving induction motor and a driven alternatingeurrent generator, an auxiliary motor-generator set, the motor being adapted to be varied in speed in accordance with load conditions of the induction motor, and the generator being adapted to regulate the fre-' quency of the main generator. The regulating action is preferably made automatic,

as hereinafter set forth. In the accompanymg drawings Flgures and 3 are dlagrammatic views of complete .systems of control embodying my invention and Figs 2 and 4 are diagrammatic views of modifications of certain portions of the respective systems shown in Figs. 1 and 3.

Referring to Fig. 1, the system here shown comprises a suitable three-phase supply circuit having phase conductors A, B and C;

- a receiving circuit, such as an electric railway system, having supply conductors D and E, a driving induction motor IM that is fed from the three-phase supply circuit, a driven single phase generator G for deliv ering energy to the receiving circuit DE, and an auxiliary 1notor-generator set comprising a drivin motor AM and an exciting generator E 1, a potential transformer T that is interposed between the exciting generator- EG and the main generator G, a resistor R that is arranged for three-phase operation in connection with the auxiliary driving motor AM, and a switching device SR for manipulating the resistor R in accordance with the current 'suppliedto the motor IM. 7

The induction motor IM comprises a suitable stator winding 1 that may be connected to the three-phase supply circuit in any well known manner, and, preferably, a wound rotor 2. The main generator G may be mechanically connected to the induction mo-' tor in any suitable manner, as by a shaft 3, and comprises an armature 4 cf the commutator type, an induced or cross-field magnet winding F that is connected to the supply circuit DE and is inductively related to the armature 4;, a plurality of short-circuited working current brushes 5, and a plurality of exciting brushes 6 that are disposed in quadrature relation to the brushes 5 and are connected to the primary winding P of the transformer T.

It will be understood that the generator 'G'is not necessarily of the type herein illustrated,'but may be of other forms, as elsewhere shown. Instead of the generator being excited from its armature, as illustrated,

the field winding may be disposed on the 100 stator to perform the same function. The

armature excitation, however, has the advantage that the apparent energy, that is, the value of volt-amperes, supplied by the exciting generator is but little in excess of 105 the amount needed to overcomethe res1st ance drop ofthe exciting current in the armature.

The auxiliary driving motor'AM is here through a plurality of conductors 10, to the 115 various sections of the three-phase res1stor R.

The exciting generator EG may comprise .a stationary single-phase generating wind.- ing 11 that is connected to the secondary 123' winding S of the transformer T and a direct-current-excited rotatable fieldqnagnet structure 12 that may be connected to the auxiliary driving motor AM by means of a suitable shaft 18. It will be appreciated 125 that the auxiliar' motor-generator set will be called upon to deliver only a relatively small percentage of the total volt-ampere; delivered to or from the main motor-generator set, inasmuch as the greater portion of the 130 shown as being of the induction-motor type,

voltage producing theexciting current for the armature is supplied by itself. Consequently the'capacity ofcthe auxiliary mthe. auxiliary driving motor AM. The core tor-generator set and the operating losses in the resistor R will be particularly small,

as compared with the energy delivered to the receiving circuit DE.

The movable member 14 of the resistor B may be connected to a suitable rotatable rod or shaft 14,, to the free end of which a link member 15 is rigidly secured. A movable core member 16 is suitably mechanically connected to the link member 15 and is adapted to be acted upon by a solenoid 17 that is series-connected in one of the phase conductors'A of the three-phase supply circuit.

Assuming the various machi es illustrated.

tobe normally operating and e movable member 1 1 of the resistor R to occupy the position shown, the operation of the system may be described as follows: Ifthe energy member 16 and the switching device SR may be returned to initial position by means of a spring 16 The speed of the auxiliary motor-generator set will, consequently, be reduced, and a corresponding decrease in the frequency delivered by; the excitin gener-.

ator EG will obtain. As a result, e exciting frequency of the main enerator G, and, therefore, the frequency de ivered to the receiving circuit DE, will be correspondingly decreased. However, the total output of-the main generator G will remain substantially constant, whereby a materially increased amount of current may be derived from the receiving circuit DE without exceeding the predetermined desired maximum energy input to the driving induction motor 1M .from the three-phase supply circuit A, B, C, as hereinbefore explainedp Reference may now be hadto Fig. 2. The modified portion of the system illustrated comprises the exciting genera-tor EG the' potential transformer T; a synchronous motor SM of the familiar rotating-field type,

having its armature 1 directly connected to the three-phase supply-circuit and having the field-magnets. of its rotor 2 excited in any suitable manner (not shown); and a main generator G1. for delivering energy to the single-phase receiving circuit DE. This type of generator is preferably employed when its speed is above the corresponding synchronous speed and is of the double-feeding type, comprising a commutator-type armature 18, a main or exciting field-magnet winding F1 and an auxiliary or compensating field magnet Winding CI. The commutator cylinder of the armature 18 is provided with a pair of supply-circuit brushes 19, one of which is-connected by a conductor 20 to oneend of the transformer primary winding P. The other brush 19 is connected, through the field-magnet winding C1, to the other end of the winding P.

Another conductor 21 serves to connect an intermediate point 22 of the primary winding P to a point 23 that lies between the field-magnet winding C1 and the armature, thus providin the well-known double-fed connection. he exciting field winding F1 is connected to the terminals of the generating winding 11 of the exciting generator EG, while the secondary winding S of the transformer T is directly connected to the receiving circuit DE. Whereas Fig. 2 shows the exciting field winding F1 disposed on the stator of the generator G1, armature excitation, as illustrated in Fig. 1, may be employed, is desired.

It will be understood that the auxiliary driving motor AM and its accessories are connected to the system shown in Fig. 2 in a manner similar to that illustrated in Fig. 1, and that the operation of the system corresponds exactly to the operation described in connection with the preceding figure; such being the case, no further exposition is deemed necessary. here. Inasmuch as, ac cording to my invention, it is not necessary to vary the driving motor speed to effect a change in generator frequency, a synchronous or constant-speed driving motor may satisfactorily be employed in place of an induction motor, as illustrated in Fig. 2. Consequently, a saving in first cost of installation may be effected, and moreover, if desired, power-factor correction in the poly phase supply circuit may readily be accomplished by the familiar method of varying the direct-current excitation of the synchronous motor.

' In case several main generators are connected to operate in parallel relation, they may be excited by the same exciting generator EG. or several such exciters may also be connected in'parallel relation.

It should be noted that the novel features of the generators G and G1 are preferred, but not absolutely essential, parts of my invention, and that various types of generators may be employed; and such features are fully set forth and claimed in my copending application, Serial No. 23,361, filed April 23, 1915.

Referring now to Fig. 3, the system shown 'comprises the tlhree-phase supply circuit A,

B, C; the induction motor TM; a driven amounts of field-magnet windings in cir-- polyphase main generator G2 that is adapted todeliver energy to a three-phase receiving circuit having phase-conductors J, K and L; an auxiliary motor-generator set comprising a driving motor AMl and an exciting generator EGl; and a switching device SR1 that is associated with the auxiliary motor AMl, in a manner to be set forth.

The main generator G2 is of the wellknown asynchronous type comprising a three-phase 'alternating-current generating stator winding 25 and a three-phase-wound rotor 26 that may be connected'to the in-v duction motor by means of the shaft 3.

The auxiliary driving motor AM1 is of the three-phase commutator type comprising an armature 27 that is mechanically con.- nected to the exciting generator EGl by the shaft 13 and a three-part field-magnet Winding 28. Each part of the field winding is connected to a corresponding brush member 29 of the armature 27, the brushes in this case being disposed approximately 120 apart on the commutator cylinder of the machine.

The switching device SR1 comprises a movable insulating member 30 that is provided with a plurality of suitable conducting members 31 which are severally variably connected by suitable contact fingers 32 to a plurality of taps of the field-magnetwinding portions 28, thus providing varying cuit, in accordance with load conditions of the driving induction motor 1M, as about to be described. The several contact fingers 32 are connected, through a plurality of conductors 33, to the corresponding conductors of the three-phase supply circuit.

A movable core member 34: is suitably associated with the movable' insulating member 30 of the switching device SR1 and is adapted tobe acted upon by a solenoid 35 that is series-connected in one of the phase-conductors A of the three-phase supply circuit.

The exciting generator EGl comprises a suitable three-phase commutator-type armature 36 and 'a distributed exciting fieldmagnet Winding F2. The armature 36 is provided with a plurality of brushes 37 that are severally connected by conductors 38 to equally-spaced points 39 of the field winding F2 which are non-corresponding, that is, they are not located on the same radial lines with the brushes 37, in accordance with a familiar practice, to insure effective operation of the exciting generator EGl with respect to the-main generator G2. The points 39 are severally connected to the 120 points of the rotor winding 26 by conductors 40.

device SR1 to occupy the position shown,

the operation of the system may be briefly set forth as follows:

If the energy input to the induction motor 1M attains a predetermined value for which the solenoid 35 is set, the core member 31 is actuated to move the switching device in such a. direction as to decrease the amount of the various portions of the field magnet windings that are in circuit. The speed of the auxiliary motor AMl is thereby correspondingly decreased, and the delivered frequency of the exciting generator EGl and, finally, of the main generator G2, are reduced in a proportional degree for the purpose hereinbefore described.

The portion of the system illustrated in Fig. 4 comprises the main generator G2 that is adapted to deliver three-phase energy to the receiving-circuit conductors J. K and L. and an exciting generator EG2.

The exciting generator EG2 may comprise a three-phase stator winding 41 that is suitably connected to the rotor winding 26 of the main generator G2 by conductors 42 and a rotor 43 that is preferably of the direct-current-excited type, as illustrated in Fig. 1 and Fig. 2.

Either the auxiliary driving motor AM or AMl may be employed to drive the exciting generator EG2 and the corresponding regulating apparatus Will, of course, be emplo ved. The general operation of the sysator EG2 and the main generator G2'may be arranged in two different ways, that is, the exciter may be connected to produce a rotating field in the generator. G3 that travels in the same direction or in a dire'ction opposite to that in which the rotatable member of the main generator moves. If this rotating field travels in the same direction, the frequency delivered to the receivingcircuit will equal the sum of the frequencies corresponding to the speeds of the main generator and the exciter. On the other hand, if the field produced by the exciter in the main generator travels in the direction opposite to that of the rotation of the main generator rotor, the resultant frequency will equal the difference of the frequencies that correspond to the speeds of rotation of the two machines. In either case, however. a change in the exciter frequency by reason of the change in the auxiliary. dr ving motor speed Wlll effect a corresponding variation in the frequency delivered to the receiving circuit.

I do not wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be made Without departing from the spirit and scope of my invention.

- taini I desire, therefore, that only such limita tions shall be imposed as are indicated in .the appended claims: q

I claim asmy invention:

.1. In an electrical system, the combination with a driving dynamo-electric. machine and {an alternating-current machine driven .thereby, of automatic means for varying thedelivered frequency of the driven machme in accordancewith the current supplied to the dynamo-electric machine while main ng the speed thereofsubstantially constant.

' 2. In an. electrical system, the combination with a, driving dynamo-electric machine and ,an alternating-current machine driven thereby, o f-means-for automatically vary ing the delivered frequency of the driven machine in accordance with predetermined conditions of the driving machine while maintaining,- the speed thereof substantially constant 3. In anelectrical system, the'combination with a driving dynamo-electric machine and an alternating-current machine driven thereby, of means for" automatically varying the deliveredfreque'ncy of the driven machine 1n accordance' with the load conditions of said driving machine while maintaining the speed of said machine substantially constant. 4. In an electrical system, the combination with a driving dynamo-electric machine and rdriving machineforvarying the delivered an alternating-current machine driven thereby, of dynamo electric means influenced in accordance with-the load conditions of said frequency of'the driven machine in accord- 2 an alternating current machine driven thereance with said load conditions while maintaming the-speed of said machines substan-v tially constant.

' 5. In an electrical system, the combination with a driving dynamo-electric machine and by, of an auxiliary motor, speed-controlling means therefor influenced directly in accord'ancey'with load conditions .of said driv-,

ing machine, said meansjbeing independent of the speed 'ofthe dynamo-electricmachine,

and an auxiliary generatordriven by said motor and adapted to deliver current to said first driven: machine I for varying the delivered frequencythereofin accordance with said load conditions, while maintaining the and driven machines substantially constant. 6

speed of said first driving 6; an electrical system, thecombination witha main"electric-motor, and an alterhating-current generator driven-thereby, of an auxiliary alternatlng-current. motor, speed 'controlling'means therefor actuated in accordance with load conditions offsai'd electric motor andfindependent of the speed of said main motor, and an auxiliary-current generator driven by said auxiliary motor to deliver an exciting current to-said first generation. 'with.. a chine and. an alternating-current machine driven thereby, of means automatically condriven thereby,

tor for automatically varying thedelivered frequency thereof in accordancewith said load conditions, while'maintainlng the speed of said electric motorand its driven'generator substantially constant.

7. In an electrical system,- thecombination 'With a driving dynamo-electric machine and an alternating-current machine driven thereby, of automatic means for obtaining a varithereof while maintaining a substantially constant speed andto obtain variations in said current output that are relatively dis proportionate to corresponding variations in the current input to said driving machine. 9. In an electrical system, the combination with an alternating-current motor and an.

1 alternating-current generator driven thereby,

of means comprising a dynamo-electric machine for varying the delivered frequency of 5 said generator in accordance with load-condltions of said alternating-current motorto obtainvariation of the current out ut therestantspeed and to obtain variations' in'said cnrrent output that are relatively'dispropor- 'tlbn'ate to the corresponding variations in the curre .t input to said alternating-current motor. j f

' fIOI'In" an j electrical system, the combinadriving dynamo electric matrolled bythe current supplied to the drivvaria'ble frequencyto thedriven machine to vary the frequency of the generated current thereof while-maintaining its speed substantially constant.

"11; In an electrical system, the combination with a driving dynamo-electric machine'and an alternating-current generator of means for automatically delivering a current of variable frequency to said generator in accordance with the .load conditions of said driving machine to vary the generated current frequency of the generator while maintaining the .speed thereof substantially constant. a a

'12. In an electrical system, the combina tion with an'alternating-current motor and an alternating-current generator driven thereby, of means comprising a dynamo .ing. machine for' delivering acurrent of 100 of while maintaining a substantially convarying the speed of said set in accordance with the load conditions of said alternatingcurrent motor, said main generator being adapted for armature excitation, whereby said motor-generator set may be of relatively small capacity. v

14. In an electrical system, the combina tion with a substantially constant-speed main motor, and a main alternating-current D motor having a speed-controlling winding, a variable resistor connected in circuit with said winding, means for varying said resistor in accordance with load conditions of said main motor, and an auxiliary alternatingcurrent generator driven by said auxiliary motor to deliver a current to the main gen-,

erator to effect a change in the frequency thereof, said main generator being adapted for self-excitation, whereby the auxiliary motor and auxiliary generator may be of relatively small capacity.

15. In an electrical system, the combination with a source of energy, a driving dynamo-electric machine connected to said sourceand an alternating-current generator driven by said machine, of means comprising a dynamo-electric machine for delivering a current to said alternating-current generator to regulate the frequency of the current generated thereby,

enerator driven thereby, of an auxiliary and means independen'tof theospeed of said driving machine for governing the speed of the lastnamed dynamo-electric machine in accordance with the load on the first-named dyamo-electric machine.

16. In an electrical system, the combination with a source of energy, a driving motor connected to said source and a main generator driven by said motor, oflmeans com prising a motor-generator set directly connected to said source-0f energy for governing the frequency of the current generated by said main generator and automatic means controlled in accordance with the load on said drivingmotor for governing the speed of said motor-generator set.

17. In an electrical system, the combination with a source of energy, a driving m0 tor connected to said source of, energy and a main generator driven by said motor, of means comprising a dynamo-electric machine directly energy for encrgizingsaid main generator to govern the frequency of the current produced thereby, and means for governing the speed of said dynamo-electric machine in accordance with the load on said driving motor. 7

18. In an electrical system, the combination with a set comprising adriving dynamo-electric machine and an alternating-current machine driven thereby, of means indev RUDOLF E. HELLMUND. Witnesses:

J. V. DOBSON, B. B. Burns.

connected to said source of pendent of the speed of said set for auto- 

